Electrical discharge machine ram cycle control system

Claim 2

In an electrical discharge machining apparatus having a tool electrode bearing ram longitudinally movable on a head and operable by a servo feed means to feed the electrode toward a workpiece and maintain a relatively uniform machining gap therebetween durIng normal cutting; a periodically actuated system for providing a predetermined up and down cycling of the ram to provide coolant flushing of the gap, said system comprising an upper limit switch and a spaced lower limit switch, both mounted on the machine tool head, a selectively adjustable upper and lower actuator means, each mounted on said ram and engageable respectively with the upper and lower switches for providing a retraction and a downfeed of the ram to a point proximate where the initial retraction was begun when normal cutting is required under control of said servo feed means; and a stop mounted proximate said lower switch and engageable with said lower actuator means, said lower actuator means slidable vertically on said ram each time a down cycle is completed.

Claim 3

The combination as set forth in claim 1 wherein a track is mounted on said ram and said upper and lower actuators are differentially positionable on said track to space said upper actuator in its alignment with said upper and lower limit switch to adjust the distance of retraction.

Claim 4

The combination as set forth in claim 2 wherein said upper and lower actuators are of a ferro-magnetic material, said actuators being held on said track by the force of magnetic attraction.

Claim 5

The combination as set forth in claim 1 wherein a means is operably connected to said servo feed means for adjusting the speed of retraction of said ram responsive to the actuation of the lower limit switch and the speed of downfeed of said ram responsive to the actuation of the upper limit switch.

Claim 6

The combination as set forth in claim 4 wherein said adjusting means comprises a rheostat operably connected to said servo feed means.

Claim 7

In an electrical discharge machining apparatus having a tool electrode bearing ram movable on a head and operable by an automatic servo feed means to feed the electrode tool toward a workpiece and maintain a relatively uniform machining gap therebetween during normal cutting; a system for providing a periodic up and down cycling of the ram to provide coolant flushing of the gap, said system comprising an upper limit switch and a lower limit switch spaced therefrom, both of said switches mounted on the machine tool head, an upper and a lower actuator means, each mounted on said ram, movable therewith and engageable respectively with said upper and lower limit switches, said upper switch operable to provide downfeed of said ram, said lower switch operable to enable operation of said automatic servo feed means whereby normal cutting is resumed, said lower actuator means slidable vertically on said ram, a stop means fixed proximate said lower limit switch and engageable with said lower actuator means, said lower actuator means being continuously slid upwardly as the result of each contact with said stop means, a timing means for periodically rendering the aforesaid system operable, said timing means including an electronic switch, and an adjustable time-constant circuit for controlling the triggering of said electronic switch.

Claim 8

In an electrical discharge machining apparatus having a tool electrode bearing ram movable on a head and operable by an automatic servo feed means to feed the electrode tool toward a workpiece and maintain a relatively uniform machining gap therebetween during normal cutting; a system for providing a periodic up and down cycling of the ram to provide coolant flushing of the gap, said system comprising an upper limit switch and a lower limit switch spaced therefrom, both of said switches mounted on the machine tool head, an upper and a lower actuator means, each mounted on said ram, movable therewith and engageable respectively with said upper and lower limit switches, said upper switch operable to provide downfeed of said ram, said lower switch operable to enable operation of said automatic servo feed means whereby normal cutting is resumed, said lower actuator means slidable vertically on said ram, a stop means fixed proximate said lower limit switch and engageable with said lower actuator means, said lower actuator means being continuously slid upwardly as the result of each contact with said stop means, a timing means for periodically rendering the aforesaid system operable, said timing means including an electronic switch, and an adjustable time-constant circuit for controlling the triggering of said electronic switch.

Claim 9

The combination as set forth in claim 6 wherein said electronic switch comprises a silicon controlled rectifier and a programmable unijunction transistor is operably connected to the gate electrode of said silicon controlled rectifier for periodically triggering it conductive and initiating operation of said system.

Claim 10

The combination as set forth in claim 6 wherein a track is mounted on said ram for holding said actuators, and wherein said actuators include a magnet for providing a holding force between them and said track.

Claim 11

In an electrical discharge machining apparatus having a tool electrode bearing ram movable on a head and operable by an automatic servo feed means to feed the electrode toward the workpiece and maintain a relatively uniform feeding gap therebetween during normal cutting; a system for providing periodic retraction and downfeed cycle of the ram to provide a coolant flushing of the gap, said system including an upper limit switch moUnted on the machine tool head, an actuator for said upper limit switch mounted on said ram and movable therewith, said upper limit switch operable to provide a downfeed of said ram responsive to its actuation, a timing means for periodically rendering said system operable for interrupting operation of said servo feed means and by initiating the retraction movement of said ram; and a means operatively connected to said ram and head for reenabling the operation of the automatic servo feed means at successively lower points to resume normal feeding after completion of a retraction and downfeed cycle, said last mentioned means comprising a lower limit switch mounted on said head and an actuator therefor mounted on said ram, said actuator displaceable upwardly at the end of each downfeed cycle to establish said points.

Claim 12

In an electrical discharge machining apparatus having a tool electrode bearing ram movable on a head and operable by an automatic servo feed means to feed the electrode toward the workpiece and maintain a relatively uniform feeding gap therebetween during normal cutting; a system for providing periodic retraction and downfeed cycle of the ram to provide a coolant flushing of the gap, said system including an upper limit switch moUnted on the machine tool head, an actuator for said upper limit switch mounted on said ram and movable therewith, said upper limit switch operable to provide a downfeed of said ram responsive to its actuation, a timing means for periodically rendering said system operable for interrupting operation of said servo feed means and by initiating the retraction movement of said ram; and a means operatively connected to said ram and head for reenabling the operation of the automatic servo feed means at successively lower points to resume normal feeding after completion of a retraction and downfeed cycle, said last mentioned means comprising a lower limit switch mounted on said head and an actuator therefor mounted on said ram, said actuator displaceable upwardly at the end of each downfeed cycle to establish said points.

Claim 13

The combination as set forth in claim 9 wherein said actuators are both slidably mounted on a track, said track fixed to said ram with its axis aligned with the path of movement of said ram.

Claim 14

In an electrical discharge machining apparatus having a tool electrode bearing ram longitudinally movable on a head and operable by a servo feed means to feed the electrode toward a workpiece and maintain a relatively uniform machining gap therebetween during normal cutting; a periodically actuated system for providing a predetermined up and down cycling of the ram to provide coolant flushing of the gap, said system comprising an upper limit switch and a spaced lower limit switch, both mounted on the machine tool head, a selectively adjustable upper and lower actuator means, each mounted on said ram and engageable respectively with the upper and lower switches for providing a retraction and a downfeed of the ram to a point proximate where the initial retraction was begun when normal cutting is required under control of said servo feed means; and an adjustable stop mounted proximate said lower limit switch and engageable with said lower actuator means for adjusting the distance above the workpiece at which normal cutting operation of said servo feed means is restored, said lower actuator including a lower magnetized portion engageable with said stop to provide a progressive upward sliding movement of said lower actuator as the cut in said workpiece becomes deeper.

Claim 15

In an electrical discharge machining apparatus having a tool electrode bearing ram longitudinally movable on a head and operable by a servo feed means to feed the electrode toward a workpiece and maintain a relatively uniform machining gap therebetween during normal cutting; a periodically actuated system for providing a predetermined up and down cycling of the ram to provide coolant flushing of the gap, said system comprising an upper limit switch and a spaced lower limit switch, both mounted on the machine tool head, a selectively adjustable upper and lower actuator means, each mounted on said ram and engageable respectively with the upper and lower switches for providing a retraction and a downfeed of the ram to a point proximate where the initial retraction was begun when normal cutting is required under control of said servo feed means; and an adjustable stop mounted proximate said lower limit switch and engageable with said lower actuator means for adjusting the distance above the workpiece at which normal cutting operation of said servo feed means is restored, said lower actuator including a lower magnetized portion engageable with said stop to provide a progressive upward sliding movement of said lower actuator as the cut in said workpiece becomes deeper.